Asynchronous Transfer Mode (ATM) is a packet switching network technology based on switching fixed length packets of data between transmission devices, a transmission device (hereinafter referred to as a node) comprehending a gateway, a router, and a switch, and referred to alternatively as a node, or respectively as a gateway, router, or switch.
An ATM network typically provides a number of interconnected nodes which receive data from network nodes and forward that data through other network nodes to an ultimate destination. In general, a node includes a plurality of ports that are coupled to at least one input and output line, each port connecting the node to another node of the network, and allowing for the routing of data between the connecting nodes.
ATM based networks can maintain a large number of connections per port and the task of clearing (disconnecting) all connections of a port is inefficient using the ATM Forum provided prior art. In order to clear a Virtual Channel, the ATM Forum prior art provides a message called RELEASE and a corresponding message called RELEASE COMPLETE. Well known to those skilled in the art, the RELEASE and the RELEASE COMPLETE message are each transmitted along the signaling channel between connecting nodes. A first network node issues a separate RELEASE message for each connection, and transmits the RELEASE message to connecting nodes for propagation along the network for eventual reception by a second network node. The second network node then initiates and transmits a corresponding RELEASE COMPLETE message as an acknowledge to the RELEASE message for that separate connection that is transmitted across the network to the first network node.
With reference to FIG. 1, an ATM data pathway comprises a connected gateway 102, node 104, node 106, node 108, and gateway 110, and illustratively carries an established specific connection between gateway 102 and gateway 110. If a calling party (not shown) that is connected to gateway 102, chooses to initiate a disconnect process, the calling party transmits a disconnect message to gateway 102. Gateway 102 responds to the disconnect message by initiating a RELEASE message that is transmitted from gateway 102 across the pathway to gateway 110, which responds to the reception of the RELEASE message by transmitting to gateway 102 a corresponding RELEASE COMPLETE message for only that specific connection. The RELEASE COMPLETE message transmitted across the pathway individually releases the specific connection on gateway 110, the nodes 108, 106, and 104, and the gateway 102.
Now referring to FIG. 2, an ATM network 200 includes a router 202, nodes 204, 206, 208, 210, 212, 214, and router 216, comprising a separate transmission path 1 that includes router 202-node 204-node 206-node 208-router 216; and a separate transmission path 2 that includes router 202-node 204-node 210-node 212-node 214-node 208-router 216. Suppose that there are twenty established connections between router 202 and router 216 such that the ten connections take path 1, and a remaining ten connections take path 2. Now suppose that the trunk that connects node 204 and 206 is cut, so that each of the ten connections along path 1 should be released. Currently, according to ATM Forum prior art, node 204 must send ten separate RELEASE messages, one for each connection, towards router 202, and node 206 must send ten separate RELEASE messages towards router 216 via node 208, as both node 204 and node 206 sense the cable cut. Routers 202 and 216 each send back a separate RELEASE COMPLETE message for each of the separate ten connections. Or suppose that that the trunk that connects node 212 and node 214 is cut, so that each of the ten connections along path 2 should be released. Currently, according to ATM Forum prior art, node 212 must send ten separate RELEASE messages towards router 202 via nodes 210 and 204 and node 214 must send ten separate RELEASE messages towards router 216 via nodes 214 and 208 as both node 212 and node 214 sense the cable cut. Routers 202 and 216 each send back a separate RELEASE COMPLETE message for each of the separate ten connections.
As illustrated, because the current RELEASE and RELEASE COMPLETE messages together clear only a single connection, in order to clear a port all data connections at the port must be cleared separately by issuance of multiple RELEASE and RELEASE COMPLETE messages, one pair for each connection. If there is network congestion, a connection clearance in accordance with the ATM Forum prior art may require a retransmission. Thus a single connection, while requiring a minimum of two messages, may require more than two messages per connection, and a port having more than “n” connections while requiring a minimum 2 “n” messages, may require many more messages than that number. Each RELEASE and each RELEASE COMPLETE message consumes network resources including processor time, memory time, processor bus time, node transmission bus time, and node switch time; all of which impact overall node transmission bandwidth and hence network performance.
The prior art RELEASE and RELEASE COMPLETE messages consume “n” times the resources in clearing a port having “n” active connections by requiring “n” separate message pairs, than a disconnection method and apparatus that has only a single pair of clearing messages for all the port connections. Also, because the number of ATM layer 3 messages exchanged across ATM switches is significantly reduced (by a factor of 1/“n”) for an ATM network by having 2 rather than 2 “n” messages, the cumulative task context switch time is reduced in an ATM switch processor. Also, the number of outstanding timers consuming node processor and memory time is reduced because only 1 timer is now required rather than n timers. The time for exchange of buffers between processor modules is also reduced. In a high-capacity ATM network, the reroute time is also reduced because the connections on a port can be disconnected by a single pair of messages, rather than a pair of messages for each individual connection. Also, the number of messages exchanged between nodes is reduced which reduces the congestion in a high capacity network. In a network comprising of large number of nodes, with a large number of connections (of the order of hundreds of thousand), to send/receive up to 4 messages per connection per node is an enormous burden on the network resources.